Kepler mission announces two exoplanets in the habitable "zone"

The planets are the right temperature and size to support liquid water.

The Kepler mission, a NASA project to find and profile planets outside of our solar system, has announced the discovery of two potentially habitable exosolar planets.

The planets are part of a system, Kepler-62, which is thought to contain five roughly earth-sized planets. The biggest is almost twice earth's size; the smallest slightly more than half.

That alone is notable, because the normal way the Kepler mission identifies planets is by measuring the gravitational they exert on their star. A big enough planet will pull the star slightly closer to the earth when it's on one side, and slightly further when it's on the other. That causes a minute fluctuation in the brightness of the star, measured from our planet, which the Kepler orbital observatory can sense.

But only the largest gas giants have such an effect, and while they are noteworthy finds in themselves, they aren't habitable. To find smaller planets, the mission looks at stars which have other fluctuations in light – due to planets passing in front of them. They then have to model every possible reason why those fluctuations could occur, and hope that they find that the most likely cause is exoplanets traversing the star.

The planets which they've found this way aren't just earth sized, though. Two of them, each measuring around 1.5 times the size of earth, are roughly the same distance away from their star as we are. Their orbits take a third and two thirds of an earth year each, but, because their star is less bright than our sun, they receive 1.2 and 0.4 times the light, respectively, that we do.

That will equal one hot planet and one cold one – but either of them might be in the so-called "habitable zone", where liquid water can exist. And liquid water is the only universal prerequisite we know for life.

The authors note that their method cannot tell if the planets are even rocky, as opposed to gas giants, let alone whether they actually have an atmosphere or water. But they are some of the best candidates we've found to date.

And crucially, we've found them fast. The Kepler telescope has been in orbit for around half its expected life, but it's already produced a vast amount of data to crunch. It's discovered almost 3,000 possible exoplanets, and has already found one that could have water. If the hit rate stays high, there could be many more.

Johannes Kepler, the 16th century astronomer for NASA's mission is named. Image: Hulton Archive/Getty Images

Alex Hern is a technology reporter for the Guardian. He was formerly staff writer at the New Statesman. You should follow Alex on Twitter.

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SRSLY #45: Love, Nina, Internet Histories Week, The Secret in Their Eyes

This week on the pop culture podcast, we chat Nick Hornby’s adaptation of Nina Stibbe’s literary memoir, our histories on the internet, and an Oscar-winning 2009 Argentinian thriller.

This is SRSLY, the pop culture podcast from the New Statesman. Here, you can find links to all the things we talk about in the show as well as a bit more detail about who we are and where else you can find us online.

...or subscribe in iTunes. We’re also on StitcherRSS and SoundCloud – but if you use a podcast app that we’re not appearing in, let us know.

SRSLY is hosted by Caroline Crampton and Anna Leszkiewicz, the NS’s web editor and editorial assistant. We’re on Twitter as @c_crampton and @annaleszkie, where between us we post a heady mixture of Serious Journalism, excellent gifs and regularly ask questions J K Rowling needs to answer.

The Links

Love, Nina

The first episode on iPlayer.

An interview with Nina Stibbe about the book.

Internet Histories Week

The index of all the posts in the series.

Our conversation about MSN Messenger.

The Secret in Their Eyes

The trailer.

For next week

Anna is watching 30 Rock.

If you’d like to talk to us about the podcast or make a suggestion for something we should read or cover, you can email srslypod[at]gmail.com.

You can also find us on Twitter @srslypod, or send us your thoughts on tumblr here. If you like the podcast, we’d love you to leave a review on iTunes - this helps other people come across it.

We love reading out your emails. If you have thoughts you want to share on anything we’ve discussed, or questions you want to ask us, please email us on srslypod[at]gmail.com, or @ us on Twitter @srslypod, or get in touch via tumblr here. We also have Facebook now.

Our theme music is “Guatemala - Panama March” (by Heftone Banjo Orchestra), licensed under Creative Commons. 

See you next week!

PS If you missed #44, check it out here.